1. Field of the Invention
The present invention relates to an information recording/reproducing apparatus for recording or reproducing content information or the like and, more particularly, to an information recording/reproducing apparatus and method of handling, e.g., content information whose copyright is protected by inhibiting copy of the information and permitting only movement of the information.
2. Description of the Related Art
Along with the diversification of digital content information such as moving images and audio data, information recording/reproducing apparatuses with various specifications have been developed and proliferated to handle such information. With these apparatuses, various kinds of information can easily be copied. Techniques are used to sufficiently protect the copyrights of the content information.
In, e.g., digital broadcasting, content information having copyright information “copy once” that permits recording of only one generation is sometimes broadcast. When this content information is received by a receiver incorporating a hard disk drive and recorded in the hard disk drive, the recorded content information cannot be recorded on other media anymore. The content information has copyright information “copy no more”. The hard disk drive has a high access speed and is therefore convenient. However, since the recording capacity of the hard disk is limited, content information that the user wants to keep long sometimes needs to be moved to another medium such as DVHS. Movement here means that the recorded copy-no-more content information is reproduced and recorded on another medium, and the original content information recorded in the hard disk drive is erased.
In recording by DVHS, content information is temporarily reproduced by the device (the receiver with the internal hard disk drive) that was used to record the information, and then recorded. In recording by the receiver with the internal hard disk drive, content information is generally encrypted and recorded to prevent any illicit copy. In a reproduction mode, if the content information that is kept encrypted is reproduced by the player and recorded by the recorder such as DVHS, the content information cannot be reproduced anymore by the device that has recorded the information. To prevent this, the encrypted information must be decrypted by the player and then output to the recorder in the reproduction mode. As a transmission line, IEEE 1394 or the like is used. The content information must be protected by using a protection mechanism such as DTCP (Digital Transmission Content Protection).
As a reference of such a conventional technique, Jpn. Pat. Appln. KOKAI Publication No. 2000-306328 is known. This reference discloses a recording/reproducing apparatus which handles content information such as audio data. To prevent illicit copy, a hash value is calculated and stored for a music database as the management information of content information. In the reproduction or copy mode, a hash value is calculated and compared with the above hash value, thereby confirming whether the music database is not altered. With this technique, illicit copy or reproduction of content information is prevented.
However, the prior art has the following problem in moving content information. That is, if an unexpected power supply interruption or operation error occurs in the apparatus during movement to DVHS serving as a recording medium, the moving operation is interrupted. In this case, it is reasonable to distinguish a portion that has already been reproduced in the content information from a portion that is not reproduced yet. It is preferable that when the power supply is restored, and movement is resumed, the portion reproduced cannot be moved, and only the portion that is not reproduced is handled as movable information. In the above-described prior art, however, both the portions become unmovable without such distinction.
Instead, content information may be managed in a shorter unit time. For example, when the encryption key of content information is changed every minute to make the key of a portion reproduced unusable, content information already reproduced and content information that is not reproduced yet can be managed. In this method, however, for example, 120 keys must be prepared for 120-min content information. It is very difficult to manage the key data.
In the above-described prior arts, if an unexpected power supply interruption or operation error occurs in the apparatus during reproduction (or movement) to DVHS serving as a recording medium, and the reproduction operation is interrupted, it is impossible to distinguish a portion that has already been reproduced in the content information from a portion that is not reproduced yet. That is, it is impossible to handle only the portion that is not reproduced yet as reproducible information. The entire content information becomes unreproducible.
In the method using many keys, key management is complex. In addition, the processing time increases, and a longer access time is required for random access to content information.